Thermal expansion coefficients (C.T.E.s) are characteristics of ceramic and/or refractory bodies, glazes, and glasses that are critically important for many applications, both traditional and advanced. In the case of traditional ceramics, the thermal expansion mismatch between the body and its glaze is tailored to place the glaze layer into compression, thus strengthening both the body and the glaze. For glazed ceramic materials, the C.T.E. of the glaze is usually less than the C.T.E. of the underlying body such that on cooling, the glaze contracts less than the underlying body and is thus placed in compression. Correspondingly, the underlying body is placed in tension. In general, when a glaze is in compression, the glaze is considered to “fit” the body. If the glaze has a greater C.T.E. than the body, the glaze is placed in tension and will crack on cooling forming the glaze defect of crazing. It is often assumed that glaze thickness contributes to crazing but the data to date does not support this assertion. It has also been proposed that crazing is related to thermal shock, but this is similarly not supported by the data.
Measuring the thermal expansion coefficient, however, is difficult due to a variety of factors ranging from material heterogeneities to instrumental problems. Current technology requires a bar or rod sample that is placed in an instrument and the change in length of the sample measured as a function of temperature; the slope of that line is the C.T.E. Throughout the industry, it is widely accepted that measurement of the thermal expansion coefficient, while often repeatable within a specific lab, is often not reproducible between labs. This casts doubt on the reliability of the data and makes the global use of the data problematic. In addition, C.T.E. measurement equipment is often both slow and quite expensive. In other words, current C.T.E. testing is expensive, slow and unreliable. Thus, a need remains for a relatively cheap, quick and reliable technique for determining the thermal expansion coefficient of a ceramic material. The present invention addresses this need.